The present invention relates to packer, bridge plug and frac plugs type tools used in wellbores and more particularly to retaining assemblies, such as extrusion limiters or retaining shoes, used in packer and bridge plug type tools.
In the drilling or reworking of oil wells, a great variety of downhole tools are used. For example, but not by way of limitation, it is often desirable to seal tubing or other pipe in the casing of the well, such as when it is desired to pump cement or other slurry down the tubing and force the cement or slurry around the annulus of the tubing or out into a formation. It then becomes necessary to seal the tubing with respect to the well casing and to prevent the fluid pressure of the slurry from lifting the tubing out of the well or for otherwise isolating specific zones in a well. Downhole tools referred to as packers and bridge plugs are designed for these general purposes and are well known in the art of producing oil and gas.
When it is desired to remove many of these downhole tools from a wellbore, it is frequently simpler and less expensive to mill or drill them out rather than to implement a complex retrieving operation. In milling, a milling cutter is used to grind the packer or plug, for example, or at least the outer components thereof, out of the wellbore. In drilling, a drill bit is used to cut and grind up the components of the downhole tool to remove it from the wellbore. This is a much faster operation than milling, but requires the tool to be made out of materials that can be accommodated by the drill bit. To facilitate removal of packer type tools by milling or drilling, packers and bridge plugs have been made, to the extent practical, of non-metallic materials such as engineering grade plastics and composites.
Packer tools and other wellbore isolation devices sometimes have elements that undesirably protrude radially and inadvertently contact a wellbore, a casing within a wellbore, or other object. Such contact sometimes results in damage to the packer tool and/or premature transitioning of the device from a run in configuration to a set configuration. For example, some conventional slip segments of wellbore isolation devices are held together somewhat tightly against a mandrel through the use of one or more bands. The bands may be intended to stretch or fracture when the tool is activated in order to allow deployment. However, the bands often protrude radially and, thus, offer limited resistance to inadvertent deployment when the wellbore isolation device undergoes inadvertent perturbation.